My work to this point is as follows: If $x > 0$, then [a theorem from my book] tells us that
\begin{align*}
\int_\mathbb{R} F(x) \, d\mu_F(x) &= \int_\mathbb{R} \mu_F \bigl((0, x]\bigr) \, d\mu_F(x)\\
&= \int_{\mathbb{R}} \int_{\mathbb{R}} \boldsymbol \chi_{\{ y \in \mathbb{R} \colon y \in (0, x] \}} \, d\mu_F(y) \, d\mu_F(x)\\
&=
\end{align*}
\begin{align*}
\int_\mathbb{R} F(x) \, d\mu_F(x) &= \int_\mathbb{R} \mu_F \bigl((0, x]\bigr) \, d\mu_F(x)\\
&= \int_{\mathbb{R}} \int_{\mathbb{R}} \boldsymbol \chi_{\{ y \in \mathbb{R} \colon y \in (0, x] \}} \, d\mu_F(y) \, d\mu_F(x)\\
&=
\end{align*}